FIG. 1 shows a configuration disclosed in Patent Literature 1 as a conventional example of the connector-incorporating plug of this type; in FIG. 1, reference numeral 11 denotes a main body portion, and reference numeral 12 denotes an optical connector inside in the main body portion 11. The optical connector 12 has a latch portion 12a that stops in an engaged state in a mating optical module to which it is connected. Reference numeral 13 denotes a connecting member that is connected to a mating adapter containing the optical module.